Spurred by the pressures of paper-based checking which is costly and time consuming for financial institutions and further in light of the inconvenience of maintaining accurate accounting in cash transactions, institutions have sought out and experimented with various electronic means of extending and speeding up account accessibility. To this end and to improve record keeping as well as to reduce flow of actual cash, computer technology has been applied to develop electronic funds transfer, which is essentially a process of value exchange achieved through electronic devices. Examples of electronic funds transfer equipment that have become used on a substantial basis in recent years are the Automated Clearning House (ACH), the Automated Teller Machine (ATM) and the point of sale system (POS).
To eliminate the presence of a central computer in every transaction, there has been a trend toward off-line electronic funds transfer, that is, transfer of data between portable and resident units, with only periodic downloading of data to the central computer. In Mareno U.S. Pat. No. 4,007,355, for example, cashless transactions are made between credit cards through a special interface located at each vendor station. Stuckert U.S. Pat. No. 4,277,837 is directed toward a cashless, off-line transaction system involving portable units that are carried by customers and adapted for use with data storage and transfer cards.
The Moreno and Stuckert systems have particular problems that have limited their widespread use in off-line electronic funds transfer. In Marino, no exchange of funds may be made arbitrarily because the cards carried by each user, although having funds data storage capability, have no keyboards and require a special interface apparatus to be present at each transaction. In Stuckert, cards used with the portable terminals have no display; a separate portable terminal must be involved during each transaction. The user cannot continuously monitor his account, limiting the versatility of the system.
These problems and others were solved by Benton in U.S. Pat. No. 4,305,059 issued on Dec. 8, 1981, disclosing a modular funds transfer system wherein each user as well as vendor carries an identical portable module having a keyboard and a display. Funds are transferred between modules using a hard wire interface, and the account status stored in each module is updated following each transaction. In another patent to Benton Pat. No. 4,341,951, printed vouchers are issued by the portable module following each transaction.
The Benton approach was further refined in U.S. Pat. No. 4,454,414 to provide bidirectional optical coupling between portable funds data transfer modules, including a "hand-shaking" protocol that enables funds transfer to be completed only if a number of criteria are satisfied. These criteria include an identification check following keyboard entry by the user of a secret number and examination of the transaction amount to ensure that it falls within credit limits.
The principles developed by Benton have in the past been limited primarily to electronic funds transfer. There now exists a need, however, to build on these principles to develop a system which, in addition to providing authorization to complete a funds transfer, maintains transaction records as a function of time as well as of amount and type of each transaction. There is likewise a need to further extend and build upon these principles to apply off-line data transfer to applications other than funds transfer, such as monitoring and recording as a function of time: radiation dosage, access within a secured area, physiological data and work-time records. There is further a need to enable direct transfer of data between users off-line directly or between users over the telephone lines or transfer of data on-line between each user and a central computer.